U.S. patent number 9,989,019 [Application Number 15/010,743] was granted by the patent office on 2018-06-05 for fuel vapor recovery apparatus.
This patent grant is currently assigned to AISAN KOGYO KABUSHIKI KAISHA. The grantee listed for this patent is AISAN KOGYO KABUSHIKI KAISHA. Invention is credited to Katsuhiko Makino.
United States Patent |
9,989,019 |
Makino |
June 5, 2018 |
Fuel vapor recovery apparatus
Abstract
A fuel vapor recovery apparatus includes an adsorbent canister
capable of capturing fuel vapor, a vapor passage connecting the
adsorbent canister to a fuel tank. In addition, the apparatus
includes an atmospheric air passage communicating the adsorbent
canister with the atmosphere, a purge passage coupling the
adsorbent canister to an intake pipe of an internal combustion
engine, a purge pump configured to generate a gas flow from the
adsorbent canister to the intake pipe through the purge passage,
and a flow control valve provided at the purge passage downstream
of the purge pump in a direction of the gas flow and configured to
regulate the gas flow through the purge passage. Further, the
apparatus includes a decompressor configured to decrease pressure
upstream of the flow control valve when the pressure upstream of
the flow control valve in the direction of the gas flow is higher
than the atmospheric pressure.
Inventors: |
Makino; Katsuhiko (Aichi-ken,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
AISAN KOGYO KABUSHIKI KAISHA |
Obu-shi, Aichi-ken |
N/A |
JP |
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Assignee: |
AISAN KOGYO KABUSHIKI KAISHA
(Obu-Shi, Aichi-Ken, JP)
|
Family
ID: |
56850289 |
Appl.
No.: |
15/010,743 |
Filed: |
January 29, 2016 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160258389 A1 |
Sep 8, 2016 |
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Foreign Application Priority Data
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Mar 6, 2015 [JP] |
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2015-044479 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02M
25/0836 (20130101) |
Current International
Class: |
F02M
25/08 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2007-32523 |
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Feb 2007 |
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JP |
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2007-177728 |
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Jul 2007 |
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JP |
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2008-240641 |
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Oct 2008 |
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JP |
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Primary Examiner: Dallo; Joseph
Assistant Examiner: Liethen; Kurt
Attorney, Agent or Firm: Conley Rose, P.C.
Claims
What is claimed is:
1. A fuel vapor recovery apparatus comprising: an adsorbent
canister capable of capturing fuel vapor; a vapor passage
connecting the adsorbent canister to a fuel tank; an atmospheric
air passage communicating the adsorbent canister with the
atmosphere; a purge passage coupling the adsorbent canister to an
intake pipe of an internal combustion engine; a purge pump
configured to generate a gas flow from the adsorbent canister to
the intake pipe through the purge passage; a flow control valve
provided at the purge passage downstream of the purge pump in a
direction of the gas flow and configured to regulate the gas flow
through the purge passage; a pressure sensor located at the purge
passage between the flow control valve and the purge pump; and a
control unit including a memory for storing control programs and a
processor for executing the control programs, the control unit
configured to receive signals from the pressure sensor and to
detect a situation in which the pressure upstream of the flow
control valve is higher than an atmospheric pressure by using the
signals from the pressure sensor, and the control unit configured
to decrease pressure upstream of the flow control valve in the
direction of the gas flow when the pressure upstream of the flow
control valve in the direction of the gas flow is higher than the
atmospheric pressure based on the control programs, wherein the
control unit is configured to carry out at least one of decreasing
a rotation number of the purge pump, decreasing pressure in the
intake pipe of the engine, and increasing a valve opening amount of
the flow control valve in order to decrease the pressure upstream
of the flow control valve.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to Japanese patent application
serial number 2015-044479, filed Mar. 6, 2015, the contents of
which are incorporated herein by reference in their entirety for
all purposes.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND
This disclosure relates to a fuel vapor recovery apparatus
including an adsorbent canister capable of capturing fuel vapor, a
vapor passage introducing the fuel vapor produced in a fuel tank to
the adsorbent canister, an atmospheric air passage fluidly
communicating the adsorbent canister with the atmosphere, and a
purge passage introducing the fuel vapor captured in the adsorbent
canister to an intake pipe of an internal combustion engine.
Japanese Laid-Open Patent Publication No. 2007-177728 discloses a
conventional fuel vapor recovery apparatus. Referring to FIG. 6,
such conventional fuel vapor recovery apparatus 100 has an
adsorbent canister 102 capable of trapping fuel vapor, a vapor
passage 104 introducing the fuel vapor produced in a fuel tank 103
to the adsorbent canister 102, an atmospheric air passage 105
fluidly communicating the adsorbent canister 102 with the
atmosphere, and a purge passage 107 introducing the fuel vapor
captured in the adsorbent canister 102 to an intake pipe 120 of an
internal combustion engine (not shown). The purge passage 107 is
provided with a purge pump 110 for generating gas flow from the
adsorbent canister 102 through the purge passage 107 to the intake
pipe 120 of the engine. The purge passage 107 is further provided
with a flow control valve 112 downstream of the purge pump 110.
According to the above-described configuration, when the purge pump
110 is started under a condition where the engine is running, the
atmospheric air can be drawn into the adsorbent canister 102
through the atmospheric air passage 105 in order to forcibly purge
the fuel vapor captured in the adsorbent canister 102 and introduce
the fuel vapor into the intake pipe 120 of the engine. During this
operation, the flow control valve 112 can regulate a flow rate of
the gas flowing through the purge passage 107 toward the intake
pipe 120 of the engine.
The fuel vapor recovery apparatus 100 is configured such that when
the purge pump 110 provided along the purge passage 107 is driven,
the fuel vapor adsorbed in the adsorbent canister 102 is forcibly
purged by the air. Thus, there is a possibility that inner pressure
of the purge passage 107 upstream of the flow control valve 112
becomes higher than the atmospheric pressure. When the engine is
stopped under a condition where the inner pressure of the purge
passage 107 is higher than the atmospheric pressure, the inner
pressure of the adsorbent canister 102 fluidly communicating with
the purge passage 107 might become higher than the atmospheric
pressure after the purge pump 110 is stopped. Accordingly, there is
a possibility that the fuel vapor adsorbed in the adsorbent
canister 102 might flow into the atmosphere through the atmospheric
air passage 105. Therefore, there has been a need for an improved
fuel vapor recovery apparatus.
BRIEF SUMMARY
In one aspect of this disclosure, a fuel vapor recovery apparatus
includes an adsorbent canister capable of capturing fuel vapor, a
vapor passage connecting the adsorbent canister to a fuel tank, an
atmospheric air passage communicating the adsorbent canister with
the atmosphere, a purge passage coupling the adsorbent canister to
an intake pipe of an internal combustion engine, a purge pump
configured to generate a gas flow from the adsorbent canister to
the intake pipe through the purge passage, a flow control valve
provided at the purge passage downstream of the purge pump in a
direction of the gas flow and configured to regulate the gas flow
through the purge passage, and a decompressor configured to
decrease pressure upstream of the flow control valve in the
direction of the gas flow when the pressure upstream of the flow
control valve in the direction of the gas flow is higher than the
atmospheric pressure.
According to this aspect of the present disclosure, when the
pressure upstream of the flow control valve in the gas flow is
higher than the atmospheric pressure under a condition where the
gas flow from the adsorbent canister to the intake pipe of the
engine through the purge passage is generated, the decompressor
decreases the pressure upstream of the flow control valve. Thus,
while the engine is running, the pressure upstream of the flow
control valve, that is, the pressure in the purge passage, the
adsorbent canister and the fuel tank is kept equal to or lower than
the atmospheric pressure. Accordingly, when the engine and the
purge pump are stopped, the pressure upstream of the flow control
valve does not become higher than the atmosphere. Therefore, the
diffusion of the fuel vapor from the adsorbent canister to the
atmosphere through the atmospheric air passage can be prevented or
reduced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of a fuel vapor recovery apparatus
according to a first embodiment.
FIG. 2 is a schematic diagram of a part of the fuel vapor recovery
apparatus.
FIG. 3 is a map used for a decompression control of the fuel vapor
recovery apparatus according to a second embodiment.
FIG. 4 is another map used for the decompression control of the
fuel vapor recovery apparatus.
FIG. 5 is a schematic diagram of a part of the fuel vapor recovery
apparatus according to a third embodiment.
FIG. 6 is a schematic diagram of the conventional fuel vapor
recovery apparatus.
DETAILED DESCRIPTION
Each of the additional features and teachings disclosed above and
below may be utilized separately or in conjunction with other
features and teachings to provide improved fuel vapor recovery
apparatuses. Representative examples, which utilize many of these
additional features and teachings both separately and in
conjunction with one another, will now be described in detail with
reference to the attached drawings. This detailed description is
merely intended to teach a person of skilled in the art further
details for practicing preferred aspects of the present teachings
and is not intended to limit the scope of the invention. Only the
claims define the scope of the claimed invention. Therefore,
combinations of features and steps disclosed in the following
detailed description may not be necessary in the broadest sense,
and are instead taught merely to particularly describe
representative examples. Moreover, various features of the
representative examples and the dependent claims may be combined in
ways that are not specifically enumerated in order to provide
additional useful embodiments of the present teachings.
A fuel vapor recovery apparatus 20 according to a first embodiment
will be described based on FIGS. 1 and 2. Referring to FIG. 1, the
fuel vapor recovery apparatus 20 is combined with an engine system
10 for a vehicle and is configured to prevent fuel vapor produced
in a fuel tank 15 of the vehicle from leaking into the outside.
As shown in FIGS. 1 and 2, the fuel vapor recovery apparatus 20
includes an adsorbent canister 22, a vapor passage 24, a purge
passage 26 and an atmospheric air passage 28. Each of the vapor
passage 24, the purge passage 26 and the atmospheric air passage 28
is coupled to the adsorbent canister 22. The adsorbent canister 22
is filled with an adsorbent (not shown), such as an activated
carbon, for adsorbing fuel vapor produced in the fuel tank 15. The
vapor passage 24 is configured to introduce the fuel vapor from the
fuel tank 15 to the adsorbent canister 22. One end (upstream end)
of the vapor passage 24 is fluidly communicated with an air layer
in the fuel tank 15, and the other end (downstream end) of the
vapor passage 24 is fluidly communicated with the inside of the
adsorbent canister 22. The atmospheric air passage 28 is configured
to communicate the adsorbent canister 22 with the atmosphere. A
base end of the atmospheric air passage 28 is coupled to the
adsorbent canister 22, and the other end of the atmospheric air
passage 28 is open to the atmosphere at a position near a fill
opening 15h of the fuel tank 15. An air filter 28a is provided in
the middle of the atmospheric air passage 28.
The purge passage 26 is configured to introduce the fuel vapor from
the adsorbent canister 22 to an intake pipe 16 of an internal
combustion engine 14 (referred to as "engine", hereinafter). The
purge passage 26 has one end (upstream end) fluidly communicating
the inside of the adsorbent canister 22 and the other end
(downstream end) fluidly communicating the intake pipe 16
downstream of a throttle valve 17. The purge passage 26 has a purge
pump 26p, a pressure sensor 26s and a flow control valve 26v in
order from the upstream end to the downstream end. The purge pump
26p is operated based on signals output from an engine control unit
(ECU) 19 and is configured to produce a gas flow from the adsorbent
canister 22 through the purge passage 26 to the intake pipe 16 of
the engine 14 while the engine 14 is running. The pressure sensor
26s is configured to measure the inner pressure of the purge
passage 26 upstream of the flow control valve 26v and to output
pressure detection signals to the ECU 19. The flow control valve
26v is configured to regulate the flow rate of the gas flowing
through the purge passage 26 while the purge pump 26p is driven.
The flow control valve 26 is operated based on signals output from
the ECU 19.
When the engine 14 of the vehicle is stopped, the flow control
valve 26v is closed in order to block fluid communication through
the purge passage 26, and the purge pump 26p is stopped. Thus, the
fuel vapor vaporized in the fuel tank 15 is introduced into the
adsorbent canister 22 through the vapor passage 24 and is adsorbed
on the adsorbent filled in the adsorbent canister 22. Then, after
starting engine 14, when predetermined purge conditions are
satisfied, the ECU 19 performs an operation for purging the fuel
vapor adsorbed on the adsorbent in the adsorbent canister 22.
During this operation, the purge pump 26p is driven and the flow
control valve 26v is opened. Thus, negative pressure generated at
an inlet side (upstream side) of the purge pump 26p is applied to
the adsorbent canister 22, so that inner pressure of the adsorbent
canister 22 becomes negative. Accordingly, the air flows into the
adsorbent canister 22 through the atmospheric air passage 28.
Further, gases flow from the fuel tank 15 into the adsorbent
canister 22, so that the fuel tank 15 is depressurized. A mixture
of the air and the gases, flowing into the adsorbent canister 22,
purges the fuel vapor adsorbed on the adsorbent and is introduced
into the purge pump 26p through the purge passage 26 together with
the fuel vapor. Then, the mixture containing the fuel vapor is
pressurized by the purge pump 26p and is supplied to the intake
pipe 16 of the engine 14 via the flow control valve 26v and the
downstream end of the purge passage 26. That is, the fuel vapor
removed from the adsorbent filled in the adsorbent canister 22 is
introduced into the intake pipe 16 of the engine 14 together with
the air and is burned in the engine 14. During this operation, the
ECU 19 controls the opening amount of the flow control valve 26v in
order to regulate the air-fuel ratio of an air-fuel mixture
supplied to the engine 14.
When the purge pump 26p is driven, the mixture containing the fuel
vapor is pressurized by the purge pump 26p and is supplied to the
intake pipe 16 of the engine 14 via the flow control valve 26v and
the purge passage 26. During this operation, because the intake
pipe 14 of the engine 16 is fluidly communicated with the purge
passage 26, inner pressure of the purge passage 26 downstream of
the flow control valve 26v is constantly negative due to the
negative pressure in the intake pipe 16. Whereas, although the
negative pressure in the intake pipe 16 of the engine 14 is applied
to the purge passage 26 upstream of the flow control valve 26v via
the flow control valve 26v, the inner pressure of the purge passage
26 upstream of the flow control valve 26v might be higher than the
atmospheric pressure due to discharge pressure (positive pressure)
of the purge pump 26p. When the engine 14 and the purge pump 26p
are stopped under a condition where the pressure P in the purge
passage 26 upstream of the flow control valve 26v is positive
(i.e., P>0 kPa in gauge pressure), the inner pressure of the
adsorbent canister 22 fluidly communicating the purge passage 26
might become positive. Thus, there is a possibility that the fuel
vapor trapped in the adsorbent canister 22 may diffuse to the
outside atmosphere through the atmospheric air passage 28. The ECU
19 is configured to perform a decompression control for preventing
such diffusion of the fuel vapor. The ECU 19 includes a memory for
storing control programs and a processor for executing the control
program, so that the decompression control is operated based on the
control programs stored in the memory of the ECU 19.
That is, the ECU 19 monitors the pressure in the purge passage 26
upstream of the flow control valve 26v (and downstream of the purge
pump 26p) by using the pressure sensor 26s. When the pressure in
the purge passage 26 becomes positive, the ECU 19 performs the
decompression control in order to decrease the pressure in the
purge passage 26 upstream of the flow control valve 26v. The
decompression control includes decreasing the rotation number N of
the purge pump 26p (e.g., rotation number N may be the revolutions
of the purge pump 26p impeller per some unit time), increasing the
valve opening amount of the flow control valve 26v, and decreasing
the pressure in the intake pipe 16 of the engine 14.
To decrease the rotation number N of the purge pump 26p, the ECU 19
may decrease voltage applied to a driving motor of the purge pump
26p. Thus, the rotation number of the driving motor is decreased,
so that the rotation number N of the purge pump 26p is also
decreased. When the rotation number N of the purge pump 26p
decreases, the discharge pressure of the purge pump 26p decreases
such that the pressure in the purge passage 26 upstream of the flow
control valve 26v decreases. Further, when the ECU 19 increases the
valve opening amount of the flow control valve 26v, pressure loss
at the flow control valve 26v decreases. Accordingly, influence of
the negative pressure in the intake pipe 16 of the engine 14 on the
pressure in the purge passage 26 upstream of the flow control valve
26v becomes greater, so that differential pressure between the
pressure in the intake pipe 16 and the pressure in the purge
passage 26 upstream of the flow control valve 26v decreases.
Consequently, the pressure in the purge passage 26 upstream of the
flow control valve 26v decreases.
To decrease the pressure in the intake pipe 16 of the engine 14,
the ECU 19 may perform a control operation for decreasing the
circulating volume of exhaust gas or changing the circulation
timing of the exhaust gas in an exhaust gas recirculation system
(EGR), or for increasing the rotation number of the engine 14
(e.g., the rotation number of engine 14 may be the number of
revolutions of an output shaft of engine 14 per some unit time),
etc. Because the intake pipe 16 of the engine 14 is in fluid
communication with the purge passage 26, when the pressure in the
intake pipe 16 of the engine 14 is lowered, the pressure in the
purge passage 26 is also decreased. Accordingly, when the
decompression control is carried out by decreasing the pressure in
the intake pipe 16, the pressure in the purge passage 26 upstream
of the flow control valve 26v decreases.
The decompression control can be performed by carrying out any one
of decreasing the rotation number N of the purge pump 26p,
increasing the valve opening amount of the flow control valve 26v
and decreasing the pressure in the intake pipe 16 of the engine 14,
or by simultaneously or sequentially carrying out at least two of
them. Because of the decompression control, the pressure in the
purge passage 26 upstream of the flow control valve 26v can be
efficiently decreased while the purge pump 26 is running. That is,
the ECU 19 corresponds to a decompressor of this disclosure.
According to the fuel vapor recovery apparatus 20, under a
condition where gas flows from the adsorbent canister 22 to the
intake pipe 16 of the engine 14 through the purge passage 26, when
the pressure upstream of the flow control valve 26v becomes higher
than the atmospheric pressure, the ECU 19 performs the
decompression control in order to decrease the pressure upstream of
the flow control valve 26v. Thus, while the engine 14 is running,
it is able to prevent the pressure upstream of the flow control
valve 26v, i.e., the pressure in the fuel tank 15, the adsorbent
canister 22 and the purge passage 26 upstream of the flow control
valve 26v, from remaining at a higher pressure than the atmospheric
pressure. Accordingly, after the engine 14 and the purge pump 26p
are stopped, the inner pressure of the purge passage 26, the
adsorbent canister 22 and others does not become higher than the
atmospheric pressure. Therefore, the diffusion of the fuel vapor
from the adsorbent canister 22 to the atmosphere through the
atmospheric air passage 28 can be prevented or reduced. Further,
because the pressure sensor 26s is provided for measuring the
pressure in the purge passage 26 upstream of the flow control valve
26v, the pressure upstream of the flow control valve 26v can be
accurately detected.
In the first embodiment, the pressure sensor 26s is provided along
the purge passage 26 upstream of the flow control valve 26v such
that based on the pressure signals output from the pressure sensor
26s, the ECU 19 performs the decompression control by decreasing
the rotation number N of the purge pump 26p, increasing the valve
opening amount of the flow control valve 26v and/or decreasing the
pressure in the intake pipe 16 of the engine 14. Whereas, the ECU
19 can be modified to carry out the decompression control based on
a map that is prepared based on a relationship between the pressure
in the purge passage 26 upstream of the flow control valve 26v, the
rotation number N of the purge pump 26p, the negative pressure
(kPa) in the intake pipe 16 of the engine 14 and the valve opening
amount (%) of the flow control valve 26v in order to prevent the
pressure upstream of the flow control valve 26v from becoming
positive.
In a second embodiment, the ECU 19 may store a first map shown in
FIG. 3 and perform the decompression control based on the first
map. The first map of FIG. 3 shows the calculated pressure P in the
purge passage 26 upstream of the flow control valve 26v, which is
estimated based on the rotation number N of the purge pump 26p and
the valve opening amount (%) of the flow control valve 26v under a
condition where the pressure in the intake pipe 16 of the engine 14
is kept at -5 kPa. According to the first map, when the valve
opening amount of the flow control valve 26v is 22% and the
rotation number of the purge pump 26p is N1, the pressure P in the
purge passage 26 is P1 (P1>0 kPa, i.e., positive pressure), so
that the decompression control is required. In this state, by
increasing the valve opening amount of the flow control valve 26v
to 80% while keeping the rotation number of the purge pump 26p at
N1, the pressure P in the purge passage 26 is presumed to decrease
to P2 (P2<0 kPa, i.e., negative pressure). Alternatively, by
decreasing the rotation number of the purge pump 26p to N2
(N2<N1) while keeping the valve opening amount of the flow
control valve 26v at 22%, the pressure P in the purge passage 26 is
presumed to decrease to P3 (P3<0 kPa, i.e., negative
pressure).
Further, the ECU 19 may store a second map shown in FIG. 4 and
perform the decompression control based on the second map. The
second map of FIG. 4 shows the calculated pressure P in the purge
passage 26, which is estimated based on the pressure PK in the
intake pipe 16 of the engine 14 and the valve opening amount (%) of
the flow control valve 26v under a condition where the rotation
number N of the purge pump 26p is maintained constant. According to
the second map, when the valve opening amount of the flow control
valve 26v is 88% and the pressure PK in the intake pipe 16 is 0
kPa, the pressure P in the purge passage 26 is P4 (P4>0 kPa,
i.e., positive pressure), so that the decompression control is
required. In this state, by decreasing the pressure PK in the
intake pipe 16 of the engine 14 to -5 kPa while keeping the valve
opening amount of the flow control valve 26v at 88%, the pressure P
in the purge passage 26 is presumed to decrease to P6 (P6<0 kPa,
i.e., negative pressure). Further, under the condition where the
pressure PK in the intake pipe 16 of the engine 14 is -5 kPa, when
the valve opening amount of the flow control valve 26v is decreased
to 40%, the pressure in the purge passage 26 is presumed to be P5
(P6<P5<0 kPa) and thus can be kept in negative. According to
the second embodiment, the pressure P in the purge passage 26
upstream of the flow control valve 26v can be estimated depending
on the maps shown in FIGS. 3 and 4, so that the pressure sensor 26s
can be omitted in order to cut production cost of the fuel vapor
recovery apparatus 20.
Further, the above-described embodiments can be modified variously.
For example, in a third embodiment as shown in FIG. 5, the pressure
sensor 26s may be provided at the fuel tank 15 located at a
position upstream of the purge passage 26 and the adsorbent
canister 22 for detecting inner pressure of the fuel tank 15. And,
the purge pump 26p may be located along the atmospheric air passage
28 upstream of the adsorbent canister 22. In addition, the vapor
passage 24 and the purge passage 26 may be directly coupled to each
other as shown by each dashed line in FIGS. 2 and 5.
* * * * *